Two-phase thermodynamic system having a porous microstructure sheet with varying surface energy to optimize utilization of a working fluid

Abstract

A vapor-chamber that includes a porous microstructure sheet with varying surface energy across different regions to optimize utilization of a working fluid. Modulating the surface energy of the porous microstructure sheet can minimize the amount of the working fluid that becomes trapped in the condenser region(s) and maximize an aggregate thin-film evaporation area of the working fluid in the evaporator region(s). The condenser region of the vapor-chamber is treated so that the internal surfaces have low surface energy. For example, the treatment may cause the condenser region to become hydrophobic to minimize the amount of fluid that becomes trapped in the condenser. The evaporator region is treated so that the internal surfaces have high surface energy. For example, the treatment may cause the evaporator region to become hydrophilic to induce the formation of large numbers of robust (e.g., dry-out resistant) thin-film evaporation sites.

What is claimed is: 
     
       1. A thermodynamic system, comprising:
 one or more walls having inner surfaces that form a sealed cavity that contains a bi-phase fluid, the bi-phase fluid having at least a vapor fraction and a liquid fraction; 
 a plurality of ribs forming channels that extend from an evaporator region of the sealed cavity to a condenser region of the sealed cavity, the evaporator region for absorbing heat into the bi-phase fluid to convert the liquid fraction into the vapor fraction, the condenser region for dissipating the heat out of the bi-phase fluid to convert the vapor fraction into the liquid fraction; and 
 a porous microstructure sheet having a plurality of pores that individually induce the liquid fraction to form one or more thin-film evaporation regions within at least a portion of the evaporator region, wherein first internal surfaces of at least some first pores within the evaporator region have a first surface energy and second internal surfaces of at least some second pores within the condenser region have a second surface energy that is less than the first surface energy, and wherein an adiabatic region of the porous microstructure sheet has a third surface energy that is less than the first surface energy and greater than the second surface energy. 
 
     
     
       2. The thermodynamic system of  claim 1 , wherein the porous microstructure sheet is disposed over the plurality of ribs to form a boundary between a liquid flow path defined by the channels and a vapor flow path. 
     
     
       3. The thermodynamic system of  claim 1 , wherein the first surface energy is achieved by applying one or more surface treatments to the porous microstructure sheet to increase a level of hydrophilicity of the first internal surfaces of the at least some first pores. 
     
     
       4. The thermodynamic system of  claim 1 , wherein the second surface energy is achieved by applying one or more surface treatments to the porous microstructure sheet to increase a level of hydrophobicity of the second internal surfaces of the at least some second pores. 
     
     
       5. The thermodynamic system of  claim 1 , wherein the first surface energy causes the liquid fraction of the bi-phase fluid to form an acute contact angle at the first internal surfaces within the evaporator region. 
     
     
       6. The thermodynamic system of  claim 1 , wherein the second surface energy causes the liquid fraction of the bi-phase fluid to form an obtuse contact angle at the second internal surfaces within the condenser region. 
     
     
       7. The thermodynamic system of  claim 1 , wherein the porous microstructure sheet is a sintered-metal-powder sheet that is disposed over the plurality of ribs. 
     
     
       8. The thermodynamic system of  claim 1 , wherein individual pores of the plurality of pores include at least three inner walls that intersect to form at least three interior corners that attract the liquid fraction to form corresponding pairs of thin-film evaporation regions. 
     
     
       9. A thermodynamic system, comprising:
 a plurality of walls having inner surfaces that form a sealed cavity that contains a liquid fraction of a bi-phase fluid and a vapor fraction of the bi-phase fluid, the sealed cavity having an evaporator region for absorbing heat to convert the liquid fraction into the vapor fraction and a condenser region for dissipating the heat to convert the vapor fraction into the liquid fraction; 
 a liquid flow path through which the liquid fraction flows from the condenser region to the evaporator region; 
 a vapor flow path through which the vapor fraction flows from the evaporator region to the condenser region; and 
 a porous microstructure sheet having a first surface energy at first internal surfaces of at least some first pores within the evaporator region and a second surface energy at second internal surfaces of at least some second pores within the condenser region, and wherein an adiabatic region of the porous microstructure sheet has a third surface energy that is less than the first surface energy and greater than the second surface energy. 
 
     
     
       10. The thermodynamic system of  claim 9 , wherein:
 the first surface energy results from one or more first surface treatments that increase a level of hydrophilicity of the first internal surfaces of the at least some first pores, and 
 the second surface energy results from one or more second surface treatments that increase a level of hydrophobicity of the second internal surfaces of the at least some second pores. 
 
     
     
       11. The thermodynamic system of  claim 9 , wherein the first surface energy causes the liquid fraction of the bi-phase fluid to form a first contact angle at the first internal surfaces within the evaporator region, and wherein the second surface energy causes the liquid fraction of the bi-phase fluid to form a second contact angle, that is greater than the first contact angle, at the second internal surfaces within the condenser region. 
     
     
       12. The thermodynamic system of  claim 9 , wherein the porous microstructure sheet is a sintered-metal-powder sheet that has been exposed to one or more surface treatments to increase a level of hydrophilicity of the first internal surfaces of the at least some first pores. 
     
     
       13. The thermodynamic system of  claim 9 , further comprising a plurality of channels that induce capillary forces on the liquid fraction to bias movement of the liquid fraction from the condenser region to the evaporator region. 
     
     
       14. The thermodynamic system of  claim 13 , wherein the porous microstructure sheet is mechanically coupled to a top end of the plurality of channels.